Project Summary: Previous studies have shown that microbial metabolites are often the compounds most markedly altered in the disease state when comparing diseased versus healthy individuals. Recent studies also suggest that metabolites deriving from microbial transformation of dietary components have significant effects on host physiological processes such as energy metabolism, gut and immune homeostasis, neurological behavior, and vascular function. Additionally, it has been proposed that metabolomics-directed functional interventions using exogenous metabolites may play critical biological roles in cellular activities. However, there are no existing, detailed, and quantitative techniques for the measurement of a broad range of endogenous microbial metabolites, nor has there been a systematic investigation of microbial communities for their metabolic functions. To fill the existing gap of knowledge, the research program outlined in this proposal focuses on three core areas: 1) Develop advanced mass spectrometry-based metabolomics technique for sensitive, quantitative detection and broad coverage of gut microbial metabolites; 2) Develop Secondary Electrospray Ionization ? Field Asymmetric Waveform Ion Mobility Spectrometry ? High-Resolution Mass Spectrometry (SESI-FAIMS- HRMS) for the rapid detection of gut microbial volatile organic compound detection; 3) Utilizing existing samples from our collaborator's lab to validate our metabolomics methods and elucidate the functionality of catechins microbial metabolites in obese host. These three coherent areas center on the development and application of mass spectrometry-based metabolomics, volatilomics and related microbial biotechnology tools to enable functional studies of microbial metabolism and nutrition-gut microbiome-host interactions. We believe this research program has great potential to elucidate the impact of microbial metabolites on host health and diseases, and to provide guidelines for modulating these metabolites to realize the full therapeutic potential, and for targeting microbial metabolism to promote human health.